There has been known an airbag device disposed at the central part of a steering wheel of an automobile, having a display device, a multifunction switching device, or a horn switching device, equipped with an airbag cover for housing an airbag on the outside of those switches and so forth.
An airbag device GB shown in FIG. 7 by way of example is provided with a display device 6R installed at the central part of a steering wheel 50R, an airbag cover 21R for containing an airbag provided with tear lines 30R to be ruptured by a gas pressure of an inflator, disposed outside of the display device 6R, and a multifunction switching device 40R for changing over a display screen of the display device 6R, disposed on the right side of the airbag cover 21R.
FIG. 8 is a cross-sectional view of the airbag device GB shown in FIG. 7, showing a state in which the airbag device GB is inflated and expanded due to an impact imposed thereon, by a vehicle and so forth.
As shown in FIG. 8, a gas generator 60R provided with the inflator is disposed at the central part of the steering wheel 50R, a securing member 4R for securing an airbag is disposed above the gas generator 60R in the figure, and a steering shaft of an operating unit is disposed below the gas generator 60R in the figure.
An angle sensor 44R of the steering wheel 50R is provided on the steering shaft and a controller 42R receiving a signal from the angle sensor 44R transmits display information corresponding to the signal to the display device 6R, which is in contact with, and secured to the head of the securing member 4R, via a harness inserted through respective holes defined in the steering shaft, the inflator, and the securing member 4R. Reference numerals 22R, 22Ra denote an airbag and a tubular tether belt, respectively, and the airbag and the tubular tether belt are normally folded and housed in the airbag cover 21R.
In the case of the conventional airbag device GB having the display device, electrical equipment such as the multifunction switching device or the horn switching device, disposed substantially at the central part of the steering wheel, and the airbag cover disposed outside those devices, the hole for use in insertion of the harness need to be made in the steering shaft, the inflator and so forth, respectively, and therefore, a steering shaft, an inflator and so forth, commonly used in the past, cannot be adopted in this case. In consequence, there arise needs for a steering shaft, inflator and so forth, provided with a hole for exclusive use in the airbag device GB respectively, so that work for manufacturing those components becomes complex, resulting in an increase in component cost.
Patent Document 1: U.S. Pat. No. 6,739,620 B2, Specification